May 11th, 2013
Precisely following an energy trail isn’t simple. We can broadly speak of energy from the Sun that’s deposited into plants. People can eat plants such as corn to power their bodies or burn plants such as trees to power their technology. These two paths take the plant’s stored energy, use some and release remnants as heat and unspent energy. Yet how do we assess the utility of either of these paths?
Historically, and even today, people use manure as a fuel source in addition to wood. This seems like a good idea. According to the UN’s FAO, people keep almost 1.6B head of cattle and buffalo. A typical cow excretes about 30kg of manure every day. Assume manure has an energy content of 15MJ/kg. Therefore, an estimate of the amount of manure energy produced each year is 2.6e20J. Perhaps surprising, this is almost the same as the total annual human energy consumption from primary fuels.
Perhaps you are thinking that we should all switch to manure as our energy source. We would have lots of food to eat (eg beef steaks) and we would have excess energy to use. Yet, the consumption of manure as a biofuel doesn’t even register. Can you determine why this energy pathway is so neglected?
April 15th, 2013
Humans are day loving animals. Commonly, we rise with the Sun and sleep when the Sun sets. The Sun is a vibrant source of heat and light which allows our primary sense, our sense of sight, to function at its best. Being a curious animal, we’ve learned to light the night. While controlled fires gave our early ancestors some warmth and light, our technology lets us light up the night and get much enjoyment too.
Candles lit up the night on the streets of Paris in 1667. Albeit, the streets were likely fewer and shorter than today, but let’s assume 1000 candles were used to light the nights there ever since. City officials would certainly want the candles lit all night long. Say a night is 12hours long and there are 365 nights in a year. Given the 346 intervening years from then until now, then candles burning at the rate of 0.1g/min by 1000 candles for 9e7min is 9.1e9grams. Take an average energy content between beeswax and paraffin of 48kJ/g makes a total of 4.36e14 Joules. That is, one city’s candle power for about 350years amounts to the equivalent energy of an atomic bomb. That’s a lot of candle power.
From another perspective, the city of Toronto has over 160,000 street lights. Assume they remain lit for 12hours each night and that they draw on average 125W. The total is 3.2e14J annually. This shows energy consumption in one year that equals 350 years of consumption for the original. That’s quite a growth.
What might the global energy expenditure be? Over 455 cities exist with populations over 1million. If each consumed the same power as Toronto then all their street lights consume 1.4e17 Joules annually. We certainly are turning night into day, removing the need to sleep, but at quite an energy cost.
March 16th, 2013
Mother Nature is pounding Europe with another seasonal winter storm. Stories abound of traffic jams, estimated at 1600km altogether. This compares to some recent traffic jams in Russia that involved tens of thousands of vehicles spread over hundreds of kilometres of roads. Just imagine all the automobiles busy going absolutely nowhere.
While the snow is often a root cause, the temporary loss of transportation is the effect. Usually considered an inconvenience, it comes at a price. Even though the idling car isn’t moving, its engine still runs. It consumes petrol at a surprisingly high rate, equal to a moderate driving speed. By some accounts, cars are kept idling for 16minutes a day on average. Average this over the global fleet of cars for a year and the result is a chronic waste of 1e16J. This wasted energy is about equal to the energy expended when the meteor struck and created the crater in Arizona. Add to this the acute loss due to snow storms and we waste even more.
Independent transportation has certainly brought incredibly opportunity and freedom to individuals. All told we produce nearly 3.2e19J of gasoline. While only about 0.04% of gasoline production gets idled away, it’s just another example of how energy slips through our fingers to little avail. What will Mother Nature have in store as our non-renewable resources continue to dwindle?
February 7th, 2013
With a few billion years of practise, life on Earth has gotten its process down pretty well down pat. Living things make more of themselves then eventually die themselves to make way for their offspring. Recycling reigns supreme as Jostein Gaarder put it, “A hydrogen atom in a cell at the end of my nose was once part of an elephant’s trunk. A carbon atom in my cardiac muscle was once in the tail of a dinosaur.” As long as living things have access to energy and can continually reproduce then there is every reason to expect this process to continue.
But then along came humankind; very smart, very curious. By playing around with a few genetic markers, researchers have created an everlasting plant. This plant won’t die off to make room for its young. It just keeps on growing, consuming atoms and capturing energy for its narcissist self. And have the researchers ever picked a good subject, the tobacco plant. Just imagine once this genetically modified construct gets into the wild, for you know it will. Tobacco plants will push out all other indigenous species. They will never die, continually growing, consuming minerals from the ground and taking all the sunshine for themselves. The land will become covered, until a natural disaster sweeps it clean and the circle of life recommences; probably from whatever a bird drops; if any birds and plant seeds remain free of our curiosity.
Where is humankind going with this? The disruption of a process that’s been ongoing for billions of years seems a bit presumptive. Are we aiming to play with our own genetic code to have humans live forever? What would we do with an Earth where people didn’t die? The population explosion would quickly shroud the land in our immediate presence. We would consume every last mineral and every last Joule of energy for ourselves. And then what?
January 11th, 2013
A recent fire at a petrol storage facility in Hazira, Gujarat underscores the risks we accept by using natural stores of high-density energy. The fire fortunately only destroyed one of nine storage tanks but it did send the oxidation by-products of burning 5million litres of petrol straight into the air. While harmful, we deem such chronic energy losses as these fires to be a reasonable cost for accessing the energy stores.
Assuming an energy content of 34.8MJ per litre then the fire released about 1.74e14 Joules. This amount is comparable to the energy released by the Hiroshima atomic bomb but less than a typical thunderstorm. Also, it is well below India’s annual petroleum consumption of 7.1e18 Joules.
From another perspective, according to the International Tanker Owners Pollution Federation Limited, about 6.4 billion litres of crude were lost between 1970 and 2009. With crude at 38.5 MJ/litre, this amounts to 2.46e17Joules. This is comparable to the fission of one ton of uranium. While significant, it pales in comparison to the world’s annual petroleum consumption of 1.9e20Joules.
Both the loss amounts calculated above are diminutive compared to humanities consumption. That is, we can easily compensate for this chronic accidental loss of stored high-density energy. The question remains, how do we compensate when we consume all the readily available sources of this form of energy?